The invention relates to a mechanism improving the operations of an Intelligent Network (IN) for merging calls initiated by the intelligent network and for producing services to subscribers.
An intelligent network provides a subscriber of a telecommunication network--such as a wired network or a mobile telephone network--with a host of different services. These services include e.g. a Private Numbering Plan (PNP), enabling the use of private numbers, and a Personal Number which allows the users to call a specific person using the same number, irrespective of the person's location and the subscriber connection used for receiving calls. A specific numbering block is defined for PBX subscribers in the numbering domain of the exchange. One example of this kind of an intelligent network is described in the recommendations of ITU-T Q-1200 series, of which Q-1210-Q-1219 define the set of features known as CS-1 (Capability Set 1) and, correspondingly, Q-1220-Q-1229 define the set of features CS-2. The present invention suggests an improvement to the call set-up mechanism presented in recommendation Q-1214. This recommendation defines functions such as Service Control Function (SCF) and Service Switching Function (SSF). A network element performing the SCF is called a Service Control Point (SCP). Similarly, a network element performing the SSF is called a Service Switching Point (SSP).
A Basic Call State Model BCSM defined in connection with an intelligent network describes the different stages of call control and includes the points where call control can be interrupted for initiating an intelligent network service. It identifies those Event Detection Points in the call and the connection process where service logic entities of the intelligent network can have an interactive relationship with basic call and connection management features.
One of the services offered by telecommunication operators is a conference call. The problem with the general mechanisms for setting up a conference call is that they require considerable skill and care from the subscriber, because conference call set-up must be controlled using special keys # and * of the telephone set. Such problems relating to the convenience of use are often solved by means of an intelligent network architecture. The problem with CS-1 and CS-2 intelligent network architectures is that they do not include the possibility of merging call segments initiated by a Service Control Function SCF. For instance, CS-2 architecture entities CallSegmentAssociation, Call-Segment, SSF FSM and the MergeCallSegments operation in the BCSM SDL-model are not possible for calls which the service control function SCF has initiated with the operation lnitiateCallAttempt. In other words, within the ITU-T and ETSI draft recommendations this operation is not allowed, but the draft recommendations define the states in which the MergeCallSegments operation is allowed, and this situation is not one of them.